1. Field of the Invention
The present invention relates to an apparatus for controlling a motor-driven let-off motion for use in a loom, and more particularly to an apparatus for controlling desired warp feeding when the loom is in inching operation or in a normal- or reverse-rotation mode of operation.
2. Description of the Prior Art
Looms have let-off motions for feeding warp yarns and controlling them to be subjected to constant tension.
Mechanical let-off motions which are generally known in the art are of such a construction that warp yarns will be fed out even when the loom is in a reverse-rotation mode of operation. If this happens, the warp tension will be varied and at the same time the fell will be moved. For restarting the loom, therefore, the warp yarns are requried to be manually wound back, a procedure which is quite troublesome. On looming, the warp yarns are required to be loosened or tensioned at high speed. In the mechanical let-off motions, this has to be done by manually turning a handle with a considerable expenditure of labor.
With electric or motor-driven let-off motions, the warp yarns can be loosened or tensioned simply by manipulating a switch to rotate a let-off motion motor in a normal or reverse direction. Therefore, the manual labor for rotating the handle with the mechanical let-off motions can be dispensed with. However, since the number of RPM of the motor is constant at all times regardless of the diameter of warp coils on beams, the length of unreeled warp yarns varies widely dependent on the warp coil diameter. Even if the switch is turned on for a constant period of time, that is, warp feeding or rewinding is performed for a constant period of time, the length of unreeled warp yarns is greater when the warp coil diameter is larger, and is smaller when the warp coil diameter is smaller. Therefore, the motor-driven let-off motion tends to feed out or rewind the warp yarns excessively even if the switch is manually actuated for a correct interval of time.
While the warp yarns are fed out or rewound by manual switch operation or inching operation in the motor-driven let-off motion, the warp tension undergoes variations, and the unreeled or rewound length of the warp yarns cannot be controlled to a nicety.